Poly(methyl methacrylate) (PMMA) is one of the matrix polymers commonly used in gel polymer electrolytes

and has been proposed for lithium battery applications.PMMA-based gel polymer electrolytes (GPE) show high ionic conductivity at ambient temperatures.However

low thermal stability and mechanical properties with hard forming freestanding film in gel systems at high organic solvents will limit its application.In order to overcome these problems

methyl methacrylate (MMA)-maleic anhydride (MAh) (P(MMA-co-MAh) ) copolymer was prepared

in the copolymer the ring structure of MAh units can improve the thermal stability and mechanical properties

consequently

improving the thermal stability of P(MMA-co-MAh)-based gel polymer electrolytes.The copolymer of P(MMA-co-MAh) was synthesized through solution copolymerization with toluene as solvent

2

2′-azobisiobutyronitrile (AIBN) as the initiator

MMA and MAh as the monomers with the molar ratios of MMA∶MAh monomer is 1∶1 The reaction was carried out at 80℃ under nitrogen atmosphere for 8 h. The structure and properties of the copolymer were characterized by Fourier transform infrared spectroscopy (FTIR)

1H-nuclear magnetic resonance (1H-NMR)

X-ray diffraction (XRD)

gel permeation chromatography (GPC)

thermogravimetric analysis (TGA)

differential scanning calorimetry (DSC).It was found that the unsaturated bonds existed in both of MMA and MAh (1637 cm-1) disappeared in the copolymer

whereas a strong absorption peak at 950 cm-1 for O=C-O-C=O ring stretching vibration of a saturated cyclic five-membered anhydride and a peak at 1445 cm-1 for —CO—O—CH3 stretching vibration of MMA were observed in the FTIR spectrum

respectively.The 1H-NMR spectrum of P(MMA-co-MAh) copolymer showed four peaks

and the peaks at δ=2.65～3.20 and 3.5～3.8 represent the chemical shift of H for MAh groups and —COOCH3 groups

respectively

indicating the molecular structure of copolymer P(MMA-co-MAh).The molar ratios of MMA and MAh in the P(MMA-co-MAh) copolymer is 8∶1. XRD showed that the P(MMA-co-MAh) was a typical amorphous polymer

which is beneficial in improvement of ionic conductivity of its GPE.GPC resalts show that the number average molecular weight (Mn) of the copolymer is 6.40×104 and the mass average molecular weight (Mw) is 6.68×104; the molecular weight distribution (Mw/Mn) is 1.04 The TGA curves show that the thermal degradation temperature of P(MMA-co-MAh) is 300℃

which is higher than that of the pure PMMA polymer.The DSC results of the P(MMA-co-MAh) copolymer reveal that the glass transition temperature (Tg) is 121.3℃

which is higher than that of the pure PMMA.The gel polymer electrolyte was prepared from the P(MMA-co-MAh) copolymer

propylene carbonate (PC) and lithium perchlorate.It is found that the GPE can form free-standing films.The ionic conductivity is 3.0×10-5 S/cm at room temperature for 45 wt% P(MMA-co-MAh) gel copolymer enlectrolyte with 55 wt% 1 mol/L LiClO4-PC solution.The ionc conductivity for GPE of P(MMA-co-MAh) copolymer is lower than that of the gel polymer electrolytes of pure PMMA containing 50 wt% PMMA with 50 wt% 1 mol/L LiClO4-PC solution.